1. Field of the Invention
This invention relates generally to an independent moving body traversing a surface having a random orientation, and more particularly for such an apparatus that may perform tasks upon such surfaces.
2. Description of the Prior Art
Present day inspection means include eddy current and ultrasonic probes, X-ray and other penetrating radiation methods and visual inspections. Such inspection means have a wide variety of applications. Cargo containers, ship hulls and aircraft skins are just some examples of surfaces which are inspected in order to monitor their structural integrity or the contents thereof. Often, unfriendly environments such as those associated with hazardous waste containers, fuel containers and nuclear vessels prevent human entry for a visual inspection. For some situations, visual inspections can be unreliable or not repeatable.
Improvements in inspection techniques are of particular interest to the aircraft industry. Aircraft skins inflate and deflate with each cycle of pressurization on take off and depressurization on landing. The resulting stress to the aircraft skin may cause several kinds of damage. Radial cracks can develop around rivets and delamination of adhesive bonded skin joints can occur. The tendency of the skin joints to delaminate is exacerbated by corrosion. Obviously as an aircraft ages, the aircraft undergoes continued cycling and the risk of aircraft skin damage is increased. Such skin damage is exacerbated by corrosion.
The aging aircraft problem is currently being addressed in the aircraft industry through periodic inspection of known problem areas on each aircraft type. A great majority of current skin inspection activity is conducted visually by inspectors trained for the task. The remaining inspection techniques involve instruments employing eddy current probes and instruments employing ultrasonic probes. Although X-ray and other penetrating radiation methods have been used for the detection of fatigue cracks in the deep structural and rotating components below the skin (related more to flying hours than to cycles), such penetrating methods are not typically employed for commercial aviation skin inspection.
Because a majority of present inspection techniques involve manual activity, inspection results may vary due to human error and lack of concentration. Also, because present inspection techniques are conducted manually, an inspector may not perform inspections in an identical fashion each time and different inspectors may perform the inspections differently. Furthermore, the duration of manual inspections is relatively long and requires that the aircraft be out of service which can disrupt schedules. These shortcomings in manual inspections are common to all industries in which manual inspections are employed and are not limited to the aircraft industry.
U.S. Pat. No. 4,940,382 discloses "an autonomous moving body [robot] able to move a working tool at a constant speed over a surface having a random shape and orientation." Some of the uses described for the robot of the '382 patent include cleaning, pumicing, painting or decorating the outer surface of an aircraft. The robot of the '382 patent has a generally rectangular first support structure having a longitudinal axis. The '382 robot also has a second support structure movably connected to the first support structure so that the first and second support structures may move relative to one another in a direction parallel to the longitudinal axis of the first support structure. The robot of the '382 patent further has a rotatable element so that the first and second support structures may be rotated relative to one another about a vertical center axis.
U.S. Pat. No. 4,674,949 discloses a "self-contained apparatus able to move along a nonhorizontal surface." Each embodiment disclosed in the '949 patent includes a first support structure having a longitudinal axis. The '949 robot further has a second support structure in which the first and second support structure are capable of moving relative to one another in a direction parallel to the longitudinal axis of the first support structure.
Neither the '949 patent nor the '382 patent describe robots having the ability to move a first support structure and a second support structure relative to one another in a variety of directions. The '949 robot may only move bidirectionally over a linear path. The '382 robot may only move bidirectionally over a linear path and rotate about a center axis. Therefore, providing a tool directly on one of the support structures of either the '949 or '382 robot offers limited ability to manipulate the tool. An apparatus is therefore needed to offer improved mobility while performing tasks on a work surface. The apparatus should be capable of performing the tasks in a precisely repeatable manner.